Adsorption of phenol from aqueous and cyclohexane solutions on activated carbons with differentiated surface chemistry

Abstract

Adsorption of phenol on activated carbon of strongly differentiated surface chemistry from aqueous and cyclohexane solutions was studied. The role of oxygen surface groups and kind of solvent in phenol adsorption was analyzed. The research showed a decrease in phenol adsorption on the oxidized carbon from water in contrast to organic solvent. The KF parameter values estimated from the Freundlich isotherm for unmodified (C1) and oxidized material (OC1) were respectively 0.19 vs. 0.26 (mmol g–1) (L mmol–1)1/n for organic solvent and 1.03 vs. 0.76 (mmol g–1)(L mmol–1)1/n for aqueous solution. Thermal analysis (TG, DTG, DTA) was used to know the kind of interactions between carbon surface and both solvents. Temperature Programmed Desorption technique was applied for characterization of carbon surface and to recognize how sorption of cyclohexane may influence its properties, e.g. changing sorption of phenol. The thermal measurements showed that phenol adsorption process on the carbons is mainly of a physical nature. Additionally, the shift of combustion exothermic peaks on DTA curves to lower temperatures for the samples with phenol adsorbed from aqueous solutions indicated the adsorbate interactions only with graphene layers, whereas, for the samples containing phenol adsorbed from cyclohexane, interactions with oxygen groups of OC1 also occurred.